1. Field of the Invention
The present invention relates to a quantitative sensor and the manufacturing method thereof and, more particularly, to a quantitative sensor with high sensitivity and made of dual-mode film bulk acoustic resonator (FBAR).
2. Description of the Related Art
With the development in semi-conductor technology, sensing elements are improved from surface acoustic wave resonators (SAWR) to film bulk acoustic resonators (FBAR). Furthermore, a dual-mode film bulk acoustic resonator is mainly composed of two electrodes and a piezoelectric layer, which has a higher quality factor and lower loss in energy since the resonant waves are transmitted through solid parts of the dual-mode film bulk acoustic resonator, wherein a bulk process is a conventional process for manufacture of the dual-mode film bulk acoustic resonator. The bulk process may etch a rear side of a substrate of a film bulk acoustic resonator to form a structural layer, which may utilize the air nearby to serve as a reflecting layer so as to decrease loss in energy.
Furthermore, in environmental, pharmaceutical and medical fields, a sensor capable of simple operation, fast analysis, and accurate result, especially which can be applied to continuous and real time monitor for various species and samples, is always a desirable invention.
However, conventional film bulk acoustic resonators cannot be used to sense targets such as liquid or bio-samples, and thus the film bulk acoustic resonators have not been utilized to form a fluid sensor or a biosensor with high sensitivity. Therefore, it is necessary to improve the conventional film bulk acoustic resonators to provide a sensor with high sensitivity, accuracy and efficiency.